Bank's Largest Shareholder Says It Will Vote Against $4.1 Billion Capital Increase

MILAN—A clash between the management of Banca Monte dei Paschi di Siena SpA and the bank's largest shareholder threatens to throw into chaos a plan to raise cash needed to stave off its full nationalization.

The Monte dei Paschi foundation, a charitable group that is the Siena-based bank's biggest shareholder with a 34% stake, is in financial straits due to the lender's troubles, as well as the foundation's attempts to keep control...